Surface mount holding feature

ABSTRACT

An electrical connector having a metal plate which is mounted under the housing with hot riveting. Location pegs are made so that low mounting force is possible. A wafer which is black in color or has another contrasting color makes it possible for a video camera to record the true position of the terminals. The surface of the top side of the housing is suited for vacuum pick up.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to electrical connectors and moreparticularly to hold-down devices for electrical connectors.

[0003] 2. Brief Description of Prior Developments

[0004] One conventional method of positioning connectors and otherelectronic components on a printed circuit board (PCB) is by means ofsurface mount technology (SMT) through-mount or intrusive reflowedterminals. Intrusive reflow is the pre-location of carefully applieddosage amount of solder in the plated through hole such that afterreflow (and not wave solder) operation a uniformly filled soldermeniscus is formed with the terminal located in the hole. The connectormay be picked up by a vacuum nozzle or similar transport means from atape and then appropriately positioned and fixed on the PCB.

[0005] There is a need for such a device which is available on the(redundant) underside of a connector whether this connector is areceptacle or a plug connector. Unlike many other hold-down devices, themeans to activate the hold-down mechanism in association with extraneousmechanical forces is avoided. This feature can be important in order toavoid rupture of delicate multi-layer boards, and thus cause unduestresses at the terminal solder connections.

SUMMARY OF THE INVENTION

[0006] In the connector of the present invention a metal plate ismounted under the housing with hot riveting. Location pegs are made sothat low mounting force is possible. A wafer which has a dark or othercontrasting color to make it possible for a video camera to record thetrue position of the terminals. The surface of the top side of thehousing is suited for vacuum pick up.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The connector of the present invention is further described withreference to the accompanying drawings in which:

[0008]FIG. 1 is a bottom perspective view of a preferred embodiment ofthe receptacle of the present invention and a wafer used in itsplacement;

[0009]FIG. 2 is a top perspective view of the connector and wafer shownin FIG. 1;

[0010]FIG. 2a is a side elevational view of the receptacle and wafershown in FIG. 2 and a plan view of the wafer;

[0011]FIG. 2b is a bottom plan view of the receptacle and wafer shown inFIG. 2 and a PCB on which it is mounted;

[0012]FIG. 3 is a top perspective view of a PCB on which the connectorshown in FIG. 1 may be mounted;

[0013]FIG. 4 is a top perspective view of a tape carrying system holdingtwo connectors similar to that shown in FIG. 1; and

[0014]FIG. 5 is a top perspective view of a connector of FIG. 1superimposed over a PCB prior to mounting.

DETAILED DESCRIPTION OF THE DRAWINGS

[0015] Referring to FIG. 1, a METRAL receptacle which is commerciallyavailable from FCI/Berg Electronics Group, Inc. located at Etters,Pennsylvania is shown generally at numeral 10. This header includes abifurcated resilient location pin 12 and location pin 14 on theunderside 19 of the connector which includes a recessed area with aperimeter 17. This recessed area contains three hot rivet pegs 18, 20and 22. An additional feature of this connector according to the noveltyis that an appropriately stamped metal plate 16 with three circularapertures (not shown) accepts the hot rivet pegs 18, 20 and 22 whilefitting into the recessed area defined by the perimeter 17.

[0016] Extending rearwardly and downwardly from the insulation housingare a plurality of contact terminals 24 which are grouped and bent at anangle of 90 degrees to engage and pass through a wafer 26. This waferpreferably has stand-offs 28, 30, 32 and 34 with a height and locationsuch that they, or the lower surface of the wafer disturb the relativelysoft paste on opposing area after location on the printed circuit board(see FIG. 5). In addition, a channel or space 36 is located alongconnector width intermediary to the underside 19 of the connector andthe wafer 26. Its function will be explained later.

[0017] As is further evident from FIG. 2, the wafer has a plurality ofridges 38, 40 and 42 and between these ridges there are grooves whichcontain the apertures (not shown) through which the connector terminalbent leads are introduced. Such a wafer is preferably black in color tofacilitate a visual inspection of the terminals. Further, as shown sucha connector will have a flat surface 44 typically suited to vacuumpick-up by a robot assisted connector assembly on the board.

[0018] Referring to FIGS. 2a, 2 b and 3, the PCB is shown generally infragment at numeral 46. On the upper surface of the PCB are referencepads 48, 50, 52 and 54. The elongate pad 56 is positioned to be locatedopposite to the connector metal plate 16. Further, the recess 57 allowsthe free passage of the rivet peg 18, while the locating pins 12 and 14are resiliently engaged in the recesses 59 and 60. The edge of such aboard is located behind the ears as at ear 70 of this connector. Suchboards are characterized in that they are thinner towards the edges, inaddition to the surface waviness compared to the surface of the plasticunderside 19. Such problems generally result in a mutual space betweenthe connector and board. This is a significant problem which needs to beovercome, particularly when the connector length (or number ofpositions) increase. To start with prior to the reflow operation, oncethe connector sits on the PCB, the reference pads 48, 50, 52 and 54 ofthe board are in contact with the opposite four locations on theunderside 19 of the connector.

[0019] Further, the board 46 contains terminal receiving apertures 58which are plated through. As a mater of detail specific to one preferredprocess, a metal stencil (not shown) of a certain thickness withappropriately positioned apertures, is positioned over board in theconnector area. This stencil with apertures extends not only over thearea of apertures 58, but also the elongate pad area 56. Once thestencil is properly positioned and laid flat over board 46, theapertures can be filled by the soft solder paste (for example, in thearea 58, see FIG. 2a), with surface leveling to the thickness of thestencil. The stencil is removed to leave a deposit of soft solder pasteof a desired thickness and area in specified locations.

[0020] As can be seen from FIG. 1, after assembly of the metal plate 16to the recessed zone of the connector, hot rivet pegs 18, 20 and 22allow rigid fixation of this plate to the connector. The thickness ofthis plate 16 is such that its average surface is either flush orslightly under the surface level of the remaining connector underside19. The board 46 (see FIG. 5) can be compensated for by a levelingeffect on the soft paste located in the mutual space opposite to theplate 16. Once the connector assembly 10 is located on board, theterminals push through the solder deposit and enter the apertures 58.Simultaneously, the mutual space between the metal plate 16 and elongatepad 56, as previously explained, is adequately filled by the soft solderpaste. Subsequent reflow will result in a melting of solder, while thesurface tension ensures to drag the solder melt between the terminalsand plated through holes, and also between plate 16 and board. Anysurplus solder is trapped in the channel or space 36. This preventsconditions for short-circuit between adjacent terminals after reflow.

[0021] Referring to FIG. 5, it will also be appreciated that thehold-down solderable surface 56 has a belt of soft paste, its topsurface being flush with the reference surfaces 48, 50, 52 and 54. Suchreference surfaces 48, 50, 52 and 54 are important for surface mounthold-down devices due to the inherent waviness of the board in relationto the potential length (positions) of connectors, and the fact thatboards often tend to be thinner towards their edges.

[0022] Referring again to FIG. 1, usually the hold-down plate 16 islocated on the connector underside 19 within a recessed area withinperimeter 17 such that in the final assembly the surface of thishold-down plate is about 0.05 mm below the aforesaid underside surfaces.At the rear of the connector underside 19 and located in an intermediaryspace with the wafer 26, is located an open space 36. When thisconnector is lowered to engage the board, prior to reflow the resultantadditional soft paste which is displaced is trapped in the open space36. This measure is important to restrict the movement of molten solderpaste in a specific area, thus preventing undesirable short circuitswith tracks in the vicinity. Also in the connector position, thelocation pins 12 and 14 resiliently engage the holes 59 and 60 while thehot riveted peg 18 passes freely through another hole 57. The other twohot rivet pegs 20 and 22 do not need to fit holes since their locationis beyond the edge of the PCB (see FIG. 5).

[0023] Referring to FIG. 4, it will be seen that the receptacle may betransported on a tape shown generally at number 60 which has a pluralityof recesses as at recess 62 and a longitudinal axial rib 64. Receptaclesas described above such as 66 and 68 are positioned in the recesses andare then subsequently removed by vacuum pick up on their upper surfacesfor placement on a PCB.

[0024] The embodiment and method shown for a horizontal receptacleconnector may equally be adapted to a vertical positioned connector, andthis concept can equally apply to plug connectors.

[0025] It will be appreciated that a connector has been described whichis adapted to be efficiently placed on a PCB, particularly by videopositioning.

[0026] While the present invention has been described in connection withthe preferred embodiments of the various figures, it is to be understoodthat other similar embodiments may be used or modifications andadditions may be made to the described embodiment for performing thesame function of the present invention without deviating therefrom.Therefore, the present invention should not be limited to any singleembodiment, but rather construed in breadth and scope in accordance withthe recitation of the appended claims.

What is claimed is:
 1. An electrical connector having an insulativehousing and terminals and a wafer engaged with said terminals for videopositioning of said terminals.
 2. The electrical connector of claim 1wherein a metal plate is mounted beneath the housing.
 3. The electricalconnector of claim 1 wherein the connector is a receptacle.
 4. Theelectrical connector of claim 2 wherein the wafer has a side which has adark color.
 5. The electrical connector of claim 4 wherein the color ofthe dark colored side of the wafer is black.
 6. The electrical connectorof claim 1 wherein the wafer has a side which has a color whichcontrasts with the terminals.
 7. The electrical connector of claim 1wherein a side of the wafer has a color which contrasts with colors ofother elements of the connector.
 8. The electrical connector of claim 1wherein the terminals extend first axially then perpendicularly from thehousing.
 9. The electrical connector of claim 8 wherein the wafer has aplurality of transverse apertures and the terminals pass through saidapertures.
 10. The electrical connector of claim 9 wherein the wafer hasa plurality of ridges and between the ridges there are grooves throughwhich the apertures pass.
 11. The electrical connector of claim 10wherein the wafer has a side having a dark color and the ridges are inopposed relation to said side having a dark color.
 12. The electricalconnector of claim 4 wherein the wafer has an upper side from which theridges extend and a lower side which is the side having a dark color.13. The electrical connector of claim 12 wherein the dark side of thewafer is superimposed on a printed circuit board (PCB).
 14. Theelectrical connector of claim 13 wherein the metal plate is superimposedon the PCB.
 15. The electrical connector of claim 14 wherein there areapertures in the PCB and the terminals pass through said apertures. 16.The electrical connector of claim 15 wherein the connector has an upperand lower side and the metal plate on the connector housing is on thelower side.
 17. The electrical connector of claim 16 wherein there is avacuum pick up surface on the upper surface of the housing.
 18. Theelectrical connector of claim 17 wherein the metal plate on the housingis superimposed over the solder pad.
 19. The electrical connector ofclaim 18 wherein solder paste is interposed between the metal plate andthe solder pad.
 20. The electrical connector of claim 19 wherein aplurality of leveling pads are interposed between the lower side of thehousing and
 21. The electrical connector of claim 20 wherein solderpaste is interposed between the lower side of the wafer and the PCB. 22.The electrical connector of claim 21 wherein there is at least one standoff interposed between the lower side of the wafer and the PCB.
 23. Anelectrical connector comprising: (a) an insulative housing having a topand bottom side and a front and a rear end; (b) a plurality of terminalsextending from the rear side of the housing first axially thenperpendicularly; and (c) a wafer having a plurality of transverseapertures at which said wafer engages said terminals.
 24. The electricalconnector of claim 23 wherein the wafer is adapted to facilitatepositioning of the connector.
 25. The electrical connector of claim 23wherein the wafer has an upper and lower side and said lower side has adark color.
 26. The electrical connector of claim 25 wherein a metalplate is mounted beneath the housing.
 27. The electrical connector ofclaim 26 wherein said connector is mounted on a printed circuit board(PCB) having a plurality of transverse apertures and a solder pad andthe terminals pass through the apertures on the PCB and the wafer issuperimposed on the PCB and the metal plate is superimposed on thesolder pad.
 28. The electrical connector of claim 27 wherein solderpaste is interposed between the metal plate and the solder pad andbetween the wafer and the PCB.
 29. An assembly comprising: (a) a printedcircuit board (PCB) having a plurality of transverse apertures and asolder pad; and (b) an electrical connector comprising: (i) aninsulative housing having a top and bottom side and a front and a rearend; (ii) a plurality of terminals extending from the rear side of thehousing first axially then perpendicularly; and (iii) a wafer having aplurality of transverse apertures at which said wafer engages saidterminals, wherein the terminals pass through the apertures on the PCB,the wafer is superimposed on the PCB.
 30. The assembly of claim 29wherein there is a metal plate on the bottom side of the housing. 31.The assembly of claim 29 wherein the wafer has a top and bottom side andthe bottom side is dark colored.
 32. The assembly of claim 30 whereinsolder paste is interposed between the metal plate and the solder pad.